There are many types of tools used downhole. Some tools are moved repeatedly between positions for the performance of different operations. While these tools are designed to shift between the positions to accomplish downhole functions, the procedures downhole vary with time and tools that readily performed functions in multiple positions reveal a potential shortcoming. One such shortcoming can be the inability to retain a desired position throughout the duration of a particular downhole operation. In the past, locking the tool in a particular position has been tried, but those attempts created additional operating limitations. Some locks were effective against pressure variations but were not effective in resisting mechanical impacts. Some locks, when actuated hydraulically, permanently held a position of the downhole tool and could not be released.
What was needed was a lock for a downhole tool that could fix its position for a time to allow a certain procedure to take place and that could thereafter be released to allow the tool to operate in its various positions for other purposes.
The context that suggested such a desired lock assembly was a downhole tool known as a downhole valve and more specifically a model ‘RB’ Valve offered by Baker Hughes Incorporated. This downhole valve featured a J-slot mechanism between a sleeve and a mandrel. Pressure in the tubing could be cycled back and forth enough times to operate the J-slot mechanism until the mandrel, upon relief of applied pressure after a predetermined amount of cycles, could move a certain distance to allow the valve to go to the open position. In this example the valve was a ball that rotated 90°. Since this valve was actuated with pressure cycles in the tubing, it could be affected by pressure spikes in the tubing. Also, it was susceptible to mechanical impacts on the mandrel that could operate the valve out of the desired position for a specific procedure. One way this could happen is a tool string running through the mandrel could drag it to the next indexing position. Competing valves that operated on hydraulic cycling in combination with a J-slot mechanism would allow the valve to go to the open position and be locked there, but the lock was permanent so the valve could not later be closed.
Some operators, particularly in deep water, have high cost completions that need a lock that can be reset to allow injection of fluids through an open valve at high rates without concern that such a procedure will operate the valve out of an open position. Additionally, such a re-settable lock could accommodate tool strings with tight clearances to pass through without risk of moving the valve out of the desired position. Such a lock would then allow the valve position to be shifted when the specific operation that required the valve position to be locked is concluded.
Those skilled in the art will more readily appreciate the multiple applications of the described preferred embodiment below in a variety of downhole applications. In the preferred embodiment, the lock can hold members that otherwise move relatively with respect to each other when the tool changes positions to perform different functions. The relative movement can occur in one or more directions.
Many tester valves operate with annulus pressure cycles and are not vulnerable to tubing pressure spikes. The ‘RB’ Valve has some similar operating characteristics to tester valves except that it cycles on application of tubing pressure. Tester valves with J-slot mechanisms are illustrated in U.S. Pat. No. 4,667,743. A hydraulically triggered resetting lock for a tester valve that selectively disables the drive system for the mandrel is shown in U.S. Pat. No. 5,518,073. In this device, the valve can stay in the open position even with subsequent pressure cycling that can unintentionally occur. The mandrel is not mechanically restrained, rather, it is simply temporarily disabled from being further actuated by applied pressure until the drive system is again enabled. Also of related interest are U.S. Pat. No. 4,403,659 and U.S. application 2002/0066573. U.S. application 2002/0112862 shows a tester valve that can be cycled a predetermined number of times before it locks permanently closed. One way this occurs is a ratchet lock as shown in FIG. 10 and another is with a collet that can jump a hump in only a single direction as shown in the lower end of the split view in FIG. 20.
Also of interest is U.S. Pat. No. 3,762,471 that uses dual control lines and a rotating ball in a subsurface safety valve that may be locked open when a sleeve attached to the ball is forced to move under hydraulic pressure so that the ball moves into the open position and a latch is also forced by hydraulic pressure to move to lock a detent into a recess. The lock can be released by pressure applied to different ports to liberate the detent from the recess. This complex design requires two control lines and due to its complexity was difficult to manufacture economically and was not commercially successful. It also required independent movement of a latch apart from the member that operates the ball to the open position to accomplish the locking. Also related to this design is U.S. Pat. No. 4,550,780 that featured a ball type subsurface safety valve that could be locked open and released. This valve was capable of being unlocked by pressure applied to the tubing and for that reason could be subject to being unlocked by unexpected pressure surges in the tubing. Locking also required the insertion of a bridge. plug.